If they ship to Canada, those are the stores I'd use.
Don't use AZ Gardens. They send the wrong plants half the time.

Another good way, which is the best way to get the HEALTHIEST plants is to become a member of planted aquarium communities, like plantedtank.net. There is a Swap and Shop section where members sell plants and clippings, and you can get nice deals there. I have to say that plants from other members are always in better health than the ones mass-grown in the shops.

There is a great person on eBay called Aquaticmagic that ships to Canada. I have purchased nano moss balls from there, excellent service. There are many other types of plants to at real affordable prices.